Molecular epidemiology of respiratory syncytial virus transmission in childcare.

BACKGROUND: Respiratory syncytial virus (RSV) is the most important cause of serious respiratory infections in young children. No prior studies using molecular techniques to examine RSV transmission in the community childcare setting have been performed.

OBJECTIVES: We seek to characterize the molecular epidemiology of RSV transmission in childcare to evaluate the impact of RSV disease in a community-based population.

METHODS: We sequenced RSV-positive nasopharyngeal samples from a prospective longitudinal study of respiratory illnesses among children enrolled in childcare during three winter seasons. Phylogenetic analysis was performed to identify unique viral strains.

RESULTS: RSV was detected in 59 (11%) illnesses. Compared to RSV-negative illnesses, RSV-positive illnesses were associated with longer symptom duration and increased frequency of health care visits. Another respiratory virus was detected in 42 (71%) RSV-positive illnesses. RSV viral load did not differ between RSV-positive illnesses with and without another respiratory virus identified (P = 0.38). In two childcare rooms, 50% of the children had RSV detected within six days of the first case. Five (38%) of 13 illness episodes from one childcare room were sequenced and shown to be the same viral strain, suggesting rapid child-to-child transmission within the room over a 16 day period.

CONCLUSIONS: RSV is rapidly transmitted within childcare. Childcare facilities may serve as ideal sites for evaluation of new prevention strategies given the high burden of RSV disease in this population and the rapidity of RSV spread between children.